The present invention relates to improvements in apparatus for implanting pacemaker electrodes, catheters and similar slender elongated objects into the circulatory systems or cavities of animal bodies, especially human patients.
The article "Permanente Herzschrittmacherversorgung mittels perkutaner Implantationstechnik" on pages 489-494 of the German-language publication entitled "Herz/Kreislauf 10" (Nov. 10, 1978) describes an apparatus which employs a syringe with a hollow metallic needle serving for introduction of a guide wire into a selected vein (e.g., into the subclavian vein) so that the guide wire can facilitate the insertion of a plastic sleeve- or hose-like introducer with assistance from a rigid dilator. Once a portion of the introducer is properly inserted into the vein, the guide wire and the dilator are extracted so that the introducer provides an unobstructed passage for implantation of a pacemaker electrode, a catheter or a similar elongated object which is to be permanently or temporarily implanted in the body. In a final step, the introducer is severed longitudinally so as to permit its separation from the implanted object. The guide wire is normally a so-called Seldinger spiral which is caused to pass through the hollow needle of the syringe as soon as the tip of the needle has penetrated into the selected vein and as soon as the cylinder and piston of the syringe are detached from the needle. The convolutions of the Seldinger wire allow for convenient introduction of the front end portion of the introducer and of the hollow cylindrical dilator therein into the vein by rotating the dilator and the introducer around the wire. The guide wire and the dilator are thereupon withdrawn from the vein and from the introducer while the corresponding part of the body is monitored by an X-ray machine.
Extraction of the introducer upon completed implantation of a pacemaker electrode and its separation from the implanted object present problems because the exposed proximal end of the implanted pacemaker electrode carries a plug by means of which the electrode is connectable to a pacemaker. The dimensions of the plug (as measured radially of the electrode) exceed the inner diameter of the introducer so that the latter cannot be slipped over the plug. Consequently, the introducer must be severed longitudinally and/or otherwise in order to allow for its separation from the implanted electrode without the need to remove the plug or to attach the plug to the electrode upon completed implantation into the body of the patient. The aforementioned German-language publication offers two solutions, namely to separate the plug from the implanted electrode or to use shears or a similar cutting implement in order to slit the introducer longitudinally so as to allow for its separation by moving it radially of and away from the exposed section of the implanted electrode.
U.S. Pat. Nos. 4,243,050 and 4,345,606 to Littleford propose to employ a tubular introducer which is formed with a longitudinally extending slot prior to putting it to actual use. This reduces the problem of separating the introducer from the exposed section of the implanted electrode without removing the plug but such types of preslotted sleeve-like introducers present many other equally serious or even graver problems. Thus, the introducer should exhibit at least some flexibility so that it can conform to the anatomy of a patient in the region where a portion thereof is introduced into the body for the purpose of establishing a path for implantation of a pacemaker electrode or the like. The longitudinally extending slot weakens the introducer so that the latter is likely to exhibit excessive flexibility and to actually buckle prior to or during implantation of an electrode or the like. This necessitates extraction of the introducer and restarting of the entire procedure, i.e., puncturing of the vein with the needle of a syringe, insertion of a guide wire, insertion of an introducer and a dilator, and extraction of the dilator and guide wire upon completed insertion of the front end portion of the introducer into the vein. On the other hand, if the preslotted introducer is relatively stiff so that it cannot undergo excessive flexing in spite of the longitudinally extending slot therein, the material of the introducer is likely to damage the relatively soft layer of insulating material which surrounds the pacemaker electrode. In other words, the rigidity of the introducer cannot be increased at will because an excessively rigid introducer is not likely to assume an optimum shape for implantation of an electrode or the like, and such rigid introducer is likely to damage the implanted object as a result of contact between the edges bounding its slit and the insulating material on the electrode.
U.S. Pat. No. 4,243,050 to Littleford also discloses an introducer having two slotted tubes which are partially telescoped into each other. When the inner tube is completely withdrawn from the outer tube, each of these tubes can be readily separated from the exposed section of a pacemaker electrode because its longitudinally extending slot has or can have a width at least matching the diameter of the electrode. The just discussed proposal exhibits the drawback that the introducer is quite expensive and complex as well as that a lengthy manipulation is necessary to separate its components from the implanted object. Furthermore, the electrode cannot be reliably held while the inner tube of the two-piece introducer is fully extracted from the outer tube as well as that large quantities of body fluid can escape by way of the introducer during separation of its components from the exposed section of the electrode. Moreover, if the slot in the one and/or the other component of such composite introducer is too narrow, the person in charge must use shears, a scalpel or another severing implement to separate the respective component from the implanted object. The shears and scalpel are likely to damage the insulation on the implanted electrode.
German Offenlegungsschrift No. 23 43 094 of Nordstrom discloses an introducer with two longitudinally extending weakened portions which allow for separation of a longitudinally extending strip therebetween. Such introducers are expensive and their flexibility cannot be controlled with a requisite degree of accuracy.
German Gebrauchsmuster No. 71 03 368 of Braun discloses an apparatus for implantation of a flexible catheter which also employs an introducer with two longitudinally extending weakened portions.
German Gebrauchsmuster No. 79 28 830 of Technological Supply, S. A. discloses an introducer which is slotted all the way from end to end prior to actual use.